A survey on fractionation: the optimal control of distilling in batch and semibatch configurations

Since the middle of the last century, discussion about the operation of discontinuous fractionation to meet multifarious goals, such as product purity and recovery rate, by monitoring process variables including reflux or/and heat duty, is been on. The engineering practice showed intolerable events to occur; hereof the operation must be supervised, which makes it difficult to be in agreement with the batch distillation objectives. Hence, to uphold the effectuation of new operating policies into the industrial “know-how” techniques, different optimal control strategies can be conceived. The objective of this work is to offer a literature survey on the investigations of optimal control functioning for selected simple distillation column configurations employed in batch/semibatch distillation of homogeneous/reactive mixtures, as well as the approaches used in this regard. Available optimal control schemes have been reviewed in detail, emphasizing its major assets.

Preparation and characterization of abalone shells derived biological mesoporous hydroxyapatite microspheres for drug delivery

The rapid growth of the abalone industry has brought a great burden to the environment because of their inedible shells. Aiming at environmental and resource sustainability, porous microspheres of carbonate-substituted hydroxyapatite (HAP) were prepared by a hydrothermal method using abalone shells; then, they were further used as a carrier for doxorubicin (DOX) in a drug delivery system. The porous HAP microspheres were approximately 6 μm in size with a considerable specific surface area and average pore size (128.6659 cm²/g and 9.064 nm, respectively), which ensured excellent drug-handling capacity (95.542%). In addition, the pH responsiveness of the drug release system was favorable for effective in vivo drug release in an acidic tumor microenvironment. Moreover, the drug-loaded microspheres could effectively induce apoptosis of MCF-7 cells but were less cytotoxic to MC3T3-E1 cells. Because of its good biocompatibility, high drug loading capacity and controlled drug release property, the porous microspheres prepared in this experiment have potential application value in drug delivery and tumor therapy; furthermore, they make full use of abalone shells, providing environmental sustainability.

Uncovering the Atomistic Mechanism for Calcite Step Growth

Determining a complete atomic-level picture of how minerals grow from aqueous solution remains a challenge as macroscopic rates can be a convolution of many reactions. For the case of calcite (CaCO₃ ) in water, computer simulations have been used to map the complex thermodynamic landscape leading to growth of the two distinct steps, acute and obtuse, on the basal surface. The carbonate ion is found to preferentially adsorb at the upper edge of acute steps while Ca²⁺ only adsorbs after CO₃^2- . In contrast to the conventional picture, ion pairs prefer to bind at the upper edge of the step with only one ion, at most, coordinated to the step and lower terrace. Migration of the first carbonate ion to a growth site is found to be rate-limiting for kink nucleation, with this process having a lower activation energy on the obtuse step.